Each year 1.25 million people are killed worldwide in traffic accidents, including 35,000 in the US. Ninety percent are due to human error. For example, a common highway hazard occurs when heavy traffic suddenly slows down. The car ahead is frantically braking or has already stopped, but the approaching drivers from behind are still unaware of the slowdown. Often the lanes on both sides are blocked. In this case, a driver must apply the brakes rapidly to avoid a collision, but not so rapidly that the car skids or that the car behind cannot stop in time. The problem gets worse for each subsequent driver in the lane, since there is less time for each driver to react due to the accumulated delay times of all the drivers in front. An alert driver can usually avoid a collision by skillfully braking, but there are times when it is simply not possible to avoid a collision.
A second common hazard occurs when two cars are traveling in substantially the same direction, and one car gradually approaches the other from the side, such as may occur during lane-change maneuvers, or while merging onto a multilane highway, or from driver inattention, or while swerving to avoid an obstacle, or for many other causes. One or both drivers may be able to avoid a side-encroachment collision by braking or swerving, but sometimes a collision is unavoidable. Often one of the cars is in the “blind spot” of the other driver, and often one or both drivers are unaware of the hazard until too late to avoid it. Not uncommonly, one of the drivers makes matters worse by taking such strong evasive action that the vehicle starts to skid.
A third important hazard develops after a collision has already occurred. The immediate post-collision period is extremely dangerous because other vehicles may be rapidly approaching, their drivers not yet aware of the problem. Often the drivers of collided vehicles are disoriented and, at least temporarily, in no shape to manage the post-collision hazards. Often the scene is chaotic, with cars strewn across lanes at random angles. Especially in snow or fog, this may lead to a cascade sequence in which numerous vehicles unavoidably crash into the tangled pile. The risk of fire is extreme. Many accident victims are relatively unharmed in the initial accident, but are then seriously injured or killed during the post-collision period, due to secondary collisions or fire or for lack of timely assistance.
Prior art in this field includes numerous collision-avoidance schemes involving sensing the distance to the car in front and automatically applying the brakes. However, such schemes may not leave enough time for the next-following car to stop, resulting in a collision from behind. This situation becomes even more hazardous if the automatic system applies the brakes too aggressively so as to leave a large space in front, since this gives the following driver even less time to react. When a collision is unavoidable, prior-art systems generally adhere to an avoidance strategy despite its futility, which often results in worse damage and injuries than otherwise.
A further limitation of prior art collision-avoidance systems is a lack of accounting for each driver's abilities. Often an alert driver with good reflexes may be able to avoid a collision even better than the automatic system. If the automatic system takes control away from such a driver, clearly the system would not be providing a benefit of any kind. Moreover, the skilled driver will probably resent having the control taken away at the most critical moment, and will probably be angry knowing that he could have avoided the collision if the system had allowed him to do so. Such a driver would likely disable the automatic system in response, thereby losing automatic assistance in a future emergency in which he may need the help. Prior-art collision-avoidance systems are typically just simple on-or-off, one-size-fits-all systems, offering no user-adjustable features. Clearly, such a system would not work well for drivers having widely different skill levels.
What is needed is automatic means for recognizing traffic hazards, including in-lane hazards and side-encroachment hazards, and for avoiding collisions automatically when it is possible to do so, and for minimizing the harm or destructiveness of collisions when they are unavoidable. Preferably the system would also manage post-collision hazards in real time. Preferably the system would be adjustable by the driver to provide the level and type of intervention that the driver requires.